Nitric oxide in the injured spinal cord: Synthases cross-talk, oxidative stress and inflammation

Nitric oxide (NO) is a unique informational molecule involved in a variety of physiological processes in the central nervous system (CNS). It has been demonstrated that it can exert both protective and detrimental effects in several disease states of the CNS, including spinal cord injury (SCI). The effects of NO on the spinal cord depend on several factors such as: concentration of produced NO, activity of different synthase isoforrns, cellular source of production and time of release. Basically, it has been shown that low NO concentrations may play a role in physiologic processes, whereas large amounts of NO may be detrimental by increasing oxidative stress. However, this does not explain all the discrepancies evidenced studying the effects of NO in SCI models. The analysis of the different synthase isoforms, of their temporal profile of activation and cellular source has shed light on this topic. Two post-injury time intervals can be defined with reference to the NO production: immediately after injury and several hours-to-days later. The initial immediate peak of NO production after injury is due to the up-regulation of the neuronal NO synthase (nNOS) in resident spinal cord cells. The late peak is due primarily to the activity of inducible NOS (iNOS) produced by inflammatory infiltrating cells. High NO levels produced by up-regulated nNOS and NOS are neurotoxic; the down-regulation of nNOS corresponds temporally to the expression of NOS. On the bases of those evidence, therapeutic approaches should be aimed: (1) to reduce the NO-elicited damage by inhibition of specific synthases according to the temporal profile of activation; (2) by maintaining physiologic amount of NO to keep the induction of iNOS expression suppressed and avoiding ischemia/reperfusion injuries; (3) by using scavengers of oxygen and nitrogen reactive species or using inhibitors of the specific kinases. (C) 2007 Elsevier B.V. All rights reserved

Nanoparticles drug-delivery systems and antiangiogenic approaches in the treatment of gliomas

The prognosis of patients with cerebral gliomas remains noticeably poor. Total surgical resection is almost unachievable due to considerable infiltrative ability of glial cells. Furthermore, adjuvant treatments are burdened by considerable limitations. Angiogenesis is the mechanism by which new blood vessels are formed from preexisting ones, thus supporting neoplasm progression. Gliomas are characterized by extensive microvascular proliferation. The extent of neovascularization in brain tumor correlates directly with the biological aggressiveness, degree of malignancy, and clinical recurrence of the tumor. Although a plethora of molecules can act as inducers of angiogenesis, the major growth factors include members of the vascular endothelium growth factor family. The new therapeutic approaches envisage the identification of specific biomarkers involved in this process and try to inhibit them, thus slowing down the neoplastic progression. Nanoparticles (NPs) show the ability to pass the blood–brain barrier, and moreover, when suitably modified, they can bind to specific overexpressed receptors in the glial cells. As carriers, they are able to protect the therapeutic agent and allow their sustained release. In this review, we describe some NP delivery systems which target specific biomarkers to intervene in the process of angiogenesis

Molecular Investigation of DKK3 in Cerebral Ischemic/Reperfusion Injury

: Dickkopf-3 (Dkk3) is an atypical member of the Dkk family of Wnt inhibitors, which has been implicated in the pathophysiology of neurodegenerative disorders. Its role in the mechanisms of cellular degeneration and protection is still unknown. The aim of our work is to investigate the endogenous activation of the DKK3 pathway in a model of transient occlusion of the middle cerebral artery in rats. In particular, the animals were subjected to 1 h of ischemia followed by different reperfusion times (1 h, 6 h, 12 h and 24 h) to evaluate the downstream pathway and the time course of its activation. Western blot analysis showed increased Dkk3 expression in animals with the highest time of reperfusion. The increased levels of Dkk3 were accompanied by reduced Wnt3a, Frz1 and PIWI1a expression in the cytosol while FOXM1 and β-catenin decreased in the nucleus. These molecular changes led to an increase in the apoptotic pathway, as showed by the increased expression of Caspase 3 and Bax and the reduced levels of Bcl-2, and to a decrease in neurogenesis, as shown by the decreased expression of Tbr2, Ngn2 and Pax6. In the second part of the study, we decided to employ curcumin, an activator of the Wnt/β-catenin signaling, to investigate its effect on Dkk3. In particular, curcumin was administered 1 and 6 h after ischemia, and animals were sacrificed 24 h later when the expression of Dkk3 was higher. Our data displayed that curcumin administration decreased Dkk3 expression, and increased Wnt3a, Frz1 and PIWI1a levels. Well in line with these data, curcumin administration increased nuclear β-catenin and FOXM1 expression. The down-regulation of Dkk3 by curcumin led to reduced apoptosis and increased neurogenesis. Summarizing, our results showed that Dkk3 acts as an inhibitor of Wnt/β-catenin signaling during cerebral ischemia. Additionally, its inhibition and the contextual activation of the Wnt/β-catenin pathway are protective against ischemic stroke